Conventionally, a mill device is known in which coffee beans, spices, tea leaves, etc., (hereinafter referred to as an “item to be milled”) are put between rotary members such as a blade and a mortar that are opposite each other and in which these rotary members are relatively rotated to perform milling processing. However, in recent years, unlike an electrically operated type in which such rotary drive is performed with an electric motor, etc., demand for a manual mill device has been increasing because power is not necessary and the place of use is not limited. In particular, among the manual mill devices, the demand for a portable mill device is remarkably increased that is further compact and easy to carry as compared with a stationary type in which a heavy main body portion is placed on a table to perform a rotary operation.
A technology is known that in such a manual portable mill device, a milling unit storing the rotary members described above is grasped with one hand, the operating handle is rotated with the other hand and thus the opposite rotary members are relatively rotated to perform milling operation (see, for example, Patent Literature 1).
The operating handle of the manual portable mill device is securely adhered with a screw, etc., to one end of the drive shaft which is cooperatively coupled to the rotary members described above, and is generally significantly protruded laterally from the milling unit. Hence, a large space in which the mill device is accumulated is needed, and thus it is impossible to easily carry the mill device while storing it in a bag, etc., with the result that it is not always possible to secure sufficient portability. Furthermore, in order to replace components such as the consumed rotary member or to repair the milling unit, it is necessary to remove the operating handle adhered and then disassemble the milling unit, with the result that the ease of maintenance is lowered.
Hence, a technology is also known in which in order for the removability of the coupling structure of the drive shaft and the operating handle to be achieved, on the shaft center of the drive shaft, the shaft portion that is formed in the shape of a regular polygon, that is pentagonal or more in cross section, for example, a pentagonal shaft portion or a hexagonal shaft portion is formed, in which in the operating handle, the shaft hole that can be externally fitted to the shaft portion and that is formed in the shape of a regular polygon that is pentagonal or more in cross section is formed and in which the shaft hole is removably externally fitted to the shaft portion.